(Sonoma State University), the PIs and Kienle (a graduate student and postdoctoral researcher at the time) set out with one shared goal: to learn more about leopard seals. Over the course of two years, the research group studied 22 leopard seals off the Western Antarctic Peninsula, an area rapidly warming and changing. The team measured one of the largest leopard seals ever, an adult female they nicknamed “Bigonia,” who weighed 540 kg (1,190 lbs.).They weighed and measured each seal and followed each seal’s activities and dive patterns using satellite/GPS tags. Female-biased sexual dimorphism (where females are larger) is unusual among marine mammals, a diverse group that includes polar bears, whales, dolphins, seals and sea lions, but leopard seals are the most extreme example of female-biased dimorphism among the 130+ species of marine mammals.Why females are larger than males is not known, although Kienle explained other studies show that larger females are better at defending feeding areas, as well as stealing prey from smaller seals.Larger females also eat bigger, energy-rich prey, including fur seals and penguins, while males and smaller females often eat smaller prey like krill and fish. This suggests that the larger body size in adult females is beneficial and offers a selective advantage that Kienle and team will continue to explore.į rom the movement data, female leopard seals spent more time “hauled out” – or coming out of the water to rest on ice or land – than males. Two adult female leopard seals in this study spent two weeks straight hauled-out on ice in the middle of the ocean, not eating and not getting in the water.Kienle and colleagues suggest that this two-week haul-out period is when female leopard seals give birth and nurse their pup. At the end of the two weeks, females return to water and begin diving for food again, and, at the same time, they likely wean their pup.It’s a short period to spend with their pups because the leopard seal is doing all of these really energetically demanding things without any food. Another seal, however, traveled 1,700 km during that same period away from the tagging location, swimming to an island more than a thousand kilometers away.One seal only traveled 46 km from where the team worked with the seal, staying in and around islands off the Antarctic Peninsula.Male and female leopard seals swim short and long distances in both coastal and open-ocean habitats. Leopard seals of both sexes are short, shallow divers-diving to an average of 30 meters and taking three-minute-long dives. Other seals can dive thousands of meters deep and hold their breath for more than 40 minutes. ![]() However, the research team recorded the longest and deepest dive ever recorded for leopard seals made by a male nicknamed “Deadpool,” who dove to 1,256 meters for 25 minutes. “It’s interesting to see such variation in a relatively small number of animals.
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